"Sometimes when one porcupine met another face to face on a branch, they both anchored themselves with their tails, sat up on their hind legs and indulged in the most ridiculous boxing-match, ducking and slapping with their front paws, feinting and lunging, giving left hooks, uppercuts and body blows, but never once making contact. Throughout this performance (which lasted perhaps for a quarter of an hour) their expression never changed from one of bewildered and benign interest. Then as though prompted by an invisible signal, they went down on all fours, and scrambled away to different parts of the tree. I could never discover the purpose of these boxing bouts nor identify the winner, but they afforded me an immense amount of amusement."

when animals in captivity engage in repetitive movements like this, it's almost always a sign of insanity from lack of mental stimulation. I find this video to be rather sad. not cute at all. poor bored porcupine.